The program will evaluate the effect of several diets on the neurotransmitter-hormone relationship and its subsequent effect on mammary tumor genesis and growth. The effect of varied protein-fat diets fed thoughout the period of fetal, neonatal and adult development on DMBA induced, prolactin dependent, rat mammary tumors will be determined. The diets are designed as high protein (28%), moderately high fat (15%) or low-protein (8%), moderately high fat (15%) and compared to normal levels. The effect of these diets, fed throughout the neonatal period and after tumor induction, on the catecholamine and serotonin activity in specific hypothalamic nuclei will be determined. Serum prolactin and estradiol will be determined at concomitant test periods. Tumors will be evaluated morphologically and the rate of DNA (3H-thymidine) and protein (3H-leucine) synthesis determined. Non-tumor animals will be assessed for the same neurotransmitters and hormones and compared with tumor responding animals in the same dietary group.